implement user.classroom getter function

[faretek1]

Implement a method/attribute in the site.user.User class

class User:
    # <...>
    def classroom(self) -> classroom.Classroom | None:
        ... # If this is a student user, return a classroom object. If not, return None

The regular api (api.scratch.mit.edu/users/{username}) does not provide classroom information, so this would require webscraping of the user's profile page (scratch.mit.edu/users/{username})

Look for a href that follows this regular expression: \/classes\/\d*\/. if it exists within this <p class="profile-details"> tag, then the user is a student. Otherwise, they are not.